1. Field of the Invention
The present invention relates in general to Global Satellite System (GSS) receivers, and in particular to a method and apparatus for sharing circuitry between Global Positioning System (GPS) and Local Area Network (LAN) (also called “Bluetooth” or “802.11”) systems.
2. Description of the Related Art
Cellular telephony, including Personal Communication System (PCS) devices, has become commonplace. The use of such devices to provide voice, data, and other services, such as internet access, has provided many conveniences to cellular system users. Further, other wireless communications systems, such as two-way paging, trunked radio, Specialized Mobile Radio (SMR) that is used by police, fire, and paramedic departments, have also become essential for mobile communications.
A current thrust in the cellular and PCS arena is the integration of Global Positioning System (GPS) technology into cellular telephone devices and other wireless transceivers. For example, U.S. Pat. No. 5,874,914, issued to Krasner, which is incorporated by reference herein, describes a method wherein the basestation (also known as the Mobile Telephone Switching Office (MTSO)) transmits GPS satellite information, including Doppler information, to a remote unit using a cellular data link, and computing pseudoranges to the in-view satellites without receiving or using satellite ephemeris information.
This current interest in integrating GPS with cellular telephony stems from a new Federal Communications Commission (FCC) requirement that cellular telephones be locatable within 50 feet once an emergency call, such as a “911” call (also referred to as “Enhanced 911” or “E911”) is placed by a given cellular telephone. Such position data assists police, paramedics, and other law enforcement and public service personnel, as well as other agencies that may need or have legal rights to determine the cellular telephone's position. Further, GPS data that is supplied to the mobile telephone can be used by the mobile telephone user for directions, latitude and longitude positions (locations or positions) of other locations or other mobile telephones that the cellular user is trying to locate, determination of relative location of the cellular user to other landmarks, directions for the cellular user via internet maps or other GPS mapping techniques, etc. Such data can be of use for other than E911 calls, and would be very useful for cellular and PCS subscribers.
The approach in Krasner, however, is limited by the number of data links that can be connected to a GPS-dedicated data supply warehouse. The system hardware would need to be upgraded to manage the additional requirements of delivering GPS information to each of the cellular or PCS users that are requesting or requiring GPS data, which requirements would be layered on top of the requirements to handle the normal voice and data traffic being managed and delivered by the wireless system.
Further, GPS receivers in cellular telephones may not always have an unobstructed view of the sky to be able to receive a sufficient number of satellite signals to perform position calculations. The GPS receiver may need additional information, such as Doppler, ephemeris, or time aiding to determine position, or, in other situations, to determine a more accurate position for the GPS receiver.
The GPS receiver may also be in an area where a Local Area Network (LAN), or Point-to-Point radio link, can provide assistance to the GPS receiver, or provide approximate position better than or instead of GPS. Such LANs and Point-to-Point networks, also known as Bluetooth systems, are used in buildings and other areas where cellular and/or GPS signals are difficult to receive.
In order to make such GPS/Bluetooth devices possible, low power dissipation is a major design concern. Operation of two separate systems that have common circuit functions will increase power dissipation of such devices. Further, the cost and form factor (size) of such parallel systems makes them difficult and expensive to produce, as well as unwieldy in certain applications.
It can be seen, then, that there is a need in the art for combining GPS and Bluetooth systems. It can also be seen that there is a need in the art to be able to aid the GPS receiver for position determination. It can also be seen that there is a need in the art to be able to aid the GPS receiver to provide more precise position determination. It can also be seen that there is a need in the art for a large cellular system that can use and/or supply GPS information to cellular users for a number of applications, including E911 without the requirement of geographically proximate basestations.